Java Assignment Sample: Building Software with Objects, Graphics, Containers, and Animation

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1. Animate Your Code: Java Assignment Samples! Programming in Java: Building Software with Objects, Graphics, and Animation

2. Introduction Objective: Learn how to create and animate graphical objects in Java . Topics Covered: Object-Oriented Programming (OOP) in Java Java’s built-in graphics and containers Creating and animating shapes Key Features: Simple, secure, and robust Multithreading capabilities Rich API for building diverse applications

3. Understanding the Classes SimpleDraw: Manages the window and rendering Contains the main method BouncingBox: Represents a box that moves and bounces within the window DrawGraphics: Manages drawing and animating graphics on the screen

4. In the last assignment you learned how to create your own simple objects. One of the advantages of building software using objects is that it makes it relatively easy to use software components that other people have built. In this assignment, you will use the Java's built-in graphics and containers, combined with a simple framework that we provide. Add three different shapes to the initial window we provide. Requirements: Add three instances of the BouncingBox class to your window, moving in different directions. Use an ArrayList to hold them. Setup: 1.(Optional) Create a new project in Eclipse, with whatever name you want. 2.Create three classes: SimpleDraw , BouncingBox , and DrawGraphics . Copy and paste the code for these classes from below. 3.Run the example program. If Eclipse gives you trouble, open SimpleDraw and run that, as it contains the main method for the program. You should see a window that looks like the following:

5. Part 1: Drawing Graphics Open the DrawGraphics class. The draw method is what draws the contents of the window. Currently, there is a line and a square with a border around it. Feel free to remove these, if you want. Add at least three different shapes to the window. Read the API documentation for the java.awt.Graphics class to find what methods are provided. You can draw rectangles, arcs, lines, text, ovals, polygons, and, if you want to do some extra work, images. Be creative! Note: You should only modify the DrawGraphics class for this step. The other classes contain a bunch of code required to create a window in Java that you do not need to change or understand.

6. Part 2 : Containers & Animations The DrawGraphics class supports animation. The draw method gets called 20 times a second, in order to draw each individual frame. The BouncingBox class also includes animation support. To get the box to move, call setMovementVector method from the DrawGraphics constructor, providing an x and y offset. For example, the value (1, 0) moves the box to the right slowly, while (0, -2) will move it up faster. You only need to call this method once to keep it moving in that direction. In other words, don't call setMovementVector from the draw method, call it from the constructor . Add at least three boxes to your window, moving in different directions. To do this, put three BouncingBox instances in an ArrayList , as part of the DrawGraphics constructor. Then, call the draw method on each of the boxes from DrawGraphics.draw , using a loop. Optional: If you want to experiment, create your own animated object. Copy BouncingBox as a starting point, then edit the code in its draw method. You could create something with more complicated movement, and/or something that looks better than what I created in five minutes. Submission Instructions: Submit your DrawGraphics.java file via Stellar.

7. SampleDraw.java

8. import java.awt.Color ; import java.awt.Dimension ; import java.awt.Graphics ; import java.awt.Graphics2D; import java.awt.RenderingHints ; import java.awt.event.WindowAdapter ; import java.awt.event.WindowEvent ; import javax.swing.JFrame ; import javax.swing.JPanel ; /** Displays a window and delegates drawing to DrawGraphics . */ public class SimpleDraw extends JPanel implements Runnable { private static final long serialVersionUID =-7469734580960165754L; private boolean animate = true; private final int FRAME_DELAY = 50; // 50 ms = 20 FPS public static final int WIDTH = 300; public static final int HEIGHT = 300; private DrawGraphics draw; public SimpleDraw ( DrawGraphics drawer){ this.draw = drawer;

9. } /** Paint callback from Swing. Draw graphics using g. */ public void paintComponent (Graphics g){ super.paintComponent (g); // Enable anti-aliasing for better looking graphics Graphics2D g2 =(Graphics2D) g; g2.setRenderingHint( RenderingHints.KEY_ANTIALIASING , RenderingHints.VALUE_ANTIALIAS_ON ); draw.draw (g2); } /** Enables periodic repaint calls. */ public synchronized void start() { animate = true; }

10. /** Pauses animation. */ public synchronized void stop() { animate = false; } private synchronized boolean animationEnabled () { return animate; } public void run() { while (true){ if ( animationEnabled ()) { repaint(); } try { Thread.sleep (FRAME_DELAY); } catch ( InterruptedException e){ throw new RuntimeException (e); }} } public static void main(String args []) { final SimpleDraw content = new SimpleDraw (new DrawGraphics ()); JFrame frame = new JFrame ("Graphics!");

11. Color bgColor = Color.white ; frame.setBackground ( bgColor ); content.setBackground ( bgColor ); // content.setSize (WIDTH, HEIGHT); // content.setMinimumSize (new Dimension(WIDTH, HEIGHT)); content.setPreferredSize (new Dimension(WIDTH, HEIGHT)); // frame.setSize (WIDTH, HEIGHT); frame.setContentPane (content); frame.setResizable (false); frame.pack (); frame.addWindowListener (new WindowAdapter () { public void windowClosing ( WindowEvent e){ System.exit (0); } public void windowDeiconified ( WindowEvent e){ content.start (); } public void windowIconified ( WindowEvent e){ content.stop (); } }); new Thread(content).start(); frame.setVisible (true); } }

12. DrawGraphics.java

13. import java.awt.BasicStroke ; import java.awt.Color ; import java.awt.Graphics ; import java.awt.Graphics2D; public class BouncingBox { int x; int y; Color color ; int xDirection = 0; int yDirection = 0; final int SIZE = 20; / ** * Initialize a new box with its center located at ( startX , startY ), filled * with startColor . */

14. public BouncingBox ( int startX , int startY , Color startColor ){ x = startX ; y = startY ; color = startColor ; } /** Draws the box at its current position on to surface. */ public void draw(Graphics surface){ // Draw the object surface.setColor (color); surface.fillRect (x - SIZE/2, y - SIZE/2, SIZE, SIZE); surface.setColor ( Color.BLACK ); ((Graphics2D) surface). setStroke (new BasicStroke (3.0f)); surface.drawRect (x - SIZE/2, y - SIZE/2, SIZE, SIZE);

15. // If we have hit the edge and are moving in the wrong direction, reverse direction // We check the direction because if a box is placed near the wall, we would get "stuck" // rather than moving in the right direction if ((x - SIZE/2 <= 0 && xDirection < 0) || (x + SIZE/2 >= SimpleDraw.WIDTH && xDirection > 0)) { xDirection =- xDirection ; } if ((y - SIZE/2 <= 0 && yDirection < 0) || (y + SIZE/2 >= SimpleDraw.HEIGHT && yDirection > 0)) { yDirection =- yDirection ; } } public void setMovementVector ( int xIncrement , int yIncrement ){ xDirection = xIncrement ; yDirection = yIncrement ; } } // Move the center of the object each time we draw it x += xDirection ; y += yDirection ;

16. DrawGraphics.java import java.awt.Color ; import java.awt.Graphics ; public class DrawGraphics { BouncingBox box; /** Initializes this class for drawing. */ public DrawGraphics () { box = new BouncingBox (200, 50, Color.RED ); } /** Draw the contents of the window on surface. Called 20 times per second. */ public void draw(Graphics surface){ surface.drawLine (50, 50, 250, 250); box.draw (surface); } }

17. BouncingBox.java

18. import java.awt.Color ; import java.awt.Dimension ; import java.awt.Graphics ; import java.awt.Graphics2D; import java.awt.RenderingHints ; import java.awt.event.WindowAdapter ; import java.awt.event.WindowEvent ; import javax.swing.JFrame ; import javax.swing.JPanel ; /** Displays a window and delegates drawing to DrawGraphics . */ public class SimpleDraw extends JPanel implements Runnable { private static final long serialVersionUID = -7469734580960165754L; private boolean animate = true; private final int FRAME_DELAY = 50; // 50 ms = 20 FPS public static final int WIDTH = 300; public static final int HEIGHT = 300; private DrawGraphics draw;

19. public SimpleDraw ( DrawGraphics drawer) { this.draw = drawer; } /** Paint callback from Swing. Draw graphics using g. */ public void paintComponent (Graphics g) { super.paintComponent (g); // Enable anti-aliasing for better looking graphics Graphics2D g2 = (Graphics2D) g; g2.setRenderingHint( RenderingHints.KEY_ANTIALIASING , RenderingHints.VALUE_ANTIALIAS_ON ); draw.draw (g2); } /** Enables periodic repaint calls. */ public synchronized void start() { animate = true; } /** Pauses animation. */

20. public synchronized void stop() { animate = false; } private synchronized boolean animationEnabled () { return animate; } public void run() { while (true) { if ( animationEnabled ()) { repaint(); } try { Thread.sleep (FRAME_DELAY); } catch ( InterruptedException e) { throw new RuntimeException (e); } } }

21. public static void main(String args []) { final SimpleDraw content = new SimpleDraw (new DrawGraphics ()); JFrame frame = new JFrame ("Graphics!"); Color bgColor = Color.white ; frame.setBackground ( bgColor ); content.setBackground ( bgColor ); // content.setSize (WIDTH, HEIGHT); // content.setMinimumSize (new Dimension(WIDTH, HEIGHT)); content.setPreferredSize (new Dimension(WIDTH, HEIGHT)); // frame.setSize (WIDTH, HEIGHT); frame.setContentPane (content); frame.setResizable (false); frame.pack (); frame.addWindowListener (new WindowAdapter () { public void windowClosing ( WindowEvent e) { System.exit (0); } public void windowDeiconified ( WindowEvent e) { content.start (); } public void windowIconified ( WindowEvent e) { content.stop (); } });

22. new Thread(content).start(); frame.setVisible (true); } } import java.awt.BasicStroke ; import java.awt.Color ; import java.awt.Graphics ; import java.awt.Graphics2D; public class BouncingBox { int x; int y; Color color ; int xDirection = 0; int yDirection = 0; final int SIZE = 20;

23. /** Initialize a new box with its center located at ( startX , startY ), filled * with startColor . */ public BouncingBox ( int startX , int startY , Color startColor ) { x = startX ; y = startY ; color = startColor ; } /** Draws the box at its current position on to surface. */ public void draw(Graphics surface) { // Draw the object surface.setColor (color); surface.fillRect (x - SIZE/2, y - SIZE/2, SIZE, SIZE); surface.setColor ( Color.BLACK ); ((Graphics2D) surface). setStroke (new BasicStroke (3.0f)); surface.drawRect (x - SIZE/2, y - SIZE/2, SIZE, SIZE); // Move the center of the object each time we draw it x += xDirection ; y += yDirection ;

24. // If we have hit the edge and are moving in the wrong direction, reverse direction // We check the direction because if a box is placed near the wall, we would get "stuck" // rather than moving in the right direction if ((x - SIZE/2 <= 0 && xDirection < 0) || (x + SIZE/2 >= SimpleDraw.WIDTH && xDirection > 0)) { xDirection = - xDirection ; } if ((y - SIZE/2 <= 0 && yDirection < 0) || (y + SIZE/2 >= SimpleDraw.HEIGHT && yDirection > 0)) { yDirection = - yDirection ; } } public void setMovementVector ( int xIncrement , int yIncrement ) { xDirection = xIncrement ; yDirection = yIncrement ; } }

25. import java.awt.Color ; import java.awt.Graphics ; public class DrawGraphics { BouncingBox box; /** Initializes this class for drawing. */ public DrawGraphics () { box = new BouncingBox (200, 50, Color.RED ); } /** Draw the contents of the window on surface. Called 20 times per second. */ public void draw(Graphics surface) { surface.drawLine (50, 50, 250, 250); box.draw (surface); } }

26. Summary: Reviewed Java basics, OOP principles, graphics, containers, and animation Provided sample code and project ideas Next Steps: Experiment with code examples Start building your own Java applications Explore advanced Java topics and libraries Contact Information: For more help and custom programming assignments, visit programminghomeworkhelp.com